The invention is based on an electromagnet for actuating a hydraulic valve.
An electromagnet of this type for actuating a hydraulic valve was made known in DE 37 23 747 A1, which said electromagnet is designed as a single-action magnet having a pressure-tight configuration. The armature is situated in a longitudinally displaceable manner in a pressure tube filled with a pressure medium, on the outside of which said pressure tube the coil and the magnet housing are situated. In addition, a manual emergency actuation device is provided on the electromagnet, the actuating bolt of which can be actuated by hand from the outside in case of emergency or during set-up, and, when the magnet is not energized, said actuating bolt can actuate the armature and/or the valve spool by means of its section extending into the pressure tube. In order to attain a desired reduction of switching speed with distributing valves of this type and, therefore, to prevent impacts that occur during switching, a throttle is installed in the armature of the electromagnet. Said throttle is installed in a passageway in the solenoid armature, through which oil moves between the two chambers located at the ends of the armature when said armature switches. Said transfer of oil decelerates the armature motions in both directions. In combination with an adapted valve spool in the distributing valve, said armature motions are referred to as “soft-switching”. Magnets of this type are connected with the valve part in a pressure-tight manner. As a result, the solenoid armature is housed in a closed space of the “pressure tube” and is unaccessible after assembly. The diameter of the throttle must be specified before the pressure tube is closed, which means that a multitude of different valve variants and/or electromagnets results. The disadvantage of this is the fact that a customer can only order a valve having a specified throttle diameter, and he does not know if the installed throttle meets the desired requirements until a machine is operated. If changes are desired, it is often necessary to replace the entire valve and the installed electromagnet.
Furthermore, a solenoid valve is made known in DE 26 60 860 C2, on whose electromagnet a hydraulic cartridge for damping switching motions is mounted externally of the magnet housing as an extension of the pressure pipe. Although the damping can be adjusted here using a throttle screw in the hydraulic cartridge that is accessible from the outside after the electromagnet and/or the solenoid valve are installed on a machine, the electromagnet with hydraulic cartridge is extremely costly to build with an additional piston-cylinder unit with spring and a rolling membrane for delimiting the space filled with hydraulic fluid, making it unusable in many cases for reasons of cost and space. In addition, a manual emergency actuation device for the electromagnet is not included.